Evaluation of the cold island effect of the urban parks in the main urban area of Wuhan from the perspective of supply and demand

Abstract

Background: Rapid urbanization has led to a series of "urban diseases" that have garnered significant social attention. Among these, the urban heat island effect has emerged as one of the most pronounced environmental concerns, presenting formidable challenges for urban planning in terms of sustainable development and environmental livability. In this process, the construction of urban parks is particularly susceptible to discrepancies between supply and demand.

Methods: In this study, urban parks with an area of more than 3hm² in the main urban area of Wuhan were selected as research objects. Utilizing remote sensing data and urban vector data, this study applied kernel density analysis and Thiessen polygons development to assess the supply capacity of parks' cold islands from a supply perspective, and the residents' cold island demand level index from a demand perspective.

Results: The findings revealed that ① The spatial distribution of cold island supply and demand exhibited significant heterogeneity. High-supply units were strongly correlated with water body distribution, while high-demand units aligned closely with population density and POI density centers, displaying a "scattered overall, locally concentrated" pattern. ② A significant supply-demand mismatch in cold island effects was observed, with 19 units (accounting for approximately 40%) exhibiting insufficient supply relative to demand. These units were predominantly concentrated in areas with complex building environments, high population density, low vegetation coverage, and poor landscape connectivity.

Discussion and conclusions: Drawing on these results, the study established an interplay between supply and demand perspectives by applying the theory of locational entropy and proposed optimization strategy for urban parks in Wuhan, aiming to achieve "a match between supply and demand in cold islands" across varying equilibrium stages of the research units. Specific measures include: optimizing the scale and layout of existing parks, reserving green spaces for ecological restoration, strengthening the protection of blue-green ecological foundations, and establishing a blue-green cold island corridor network to enhance ecological connectivity. Our work extends the understanding of the cold island effect of urban parks, assisting urban planners in proposing more targeted and effective management strategy and measures to improve the urban thermal environment, thereby contributing to the creation of healthy, equitable, and sustainable cities.

Keywords: cold island effect; planning strategy; supply and demand evaluation; urban heat and cold islands; urban parks.

Figure 1

Distribution of the urban parks with an area of more than 3hm² in the main urban area of Wuhan.

Figure 2

Logic diagram of the supply and demand evaluation model of the urban parks’ cold island effect.

Figure 3

Process of generating Thiessen polygons from polygon elements.

Figure 4

Spatial distribution of the urban park service units in the main urban area of Wuhan; The numbers 1–48 represent the park service unit number.

Figure 5

Spatial distribution of the vegetation coverage in the main urban area of Wuhan.

Figure 6

Spatial distribution of the park accessibility in the main urban area of Wuhan.

Figure 7

Per capita park size in each park service unit in the main urban area of Wuhan.

Figure 8

(A) Spatial distribution of the cold island supply capacity; (B) The cold island supply capacity within each ring road in the study area.

Figure 9

Population density distribution in the main urban area of Wuhan.

Figure 10

POI kernel density in the main urban area of Wuhan.

Figure 11

Inversion of land surface temperature in the main urban area of Wuhan.

Figure 12

Spatial distribution of assigned values for heat island patches in the main urban area of Wuhan.

Figure 13

(A) Spatial distribution of the cold island demand index; (B) The cold island demand capacity within each ring road in the study area.

Figure 14

(A) Spatial distribution of the supply–demand relationship of cold island effect in the main urban area of Wuhan; (B) Spatial distribution of the social supply-shortage type units; (C) Spatial distribution of the ecological service-shortage type units.

Figure 15

Operational mechanism of adaptive planning structures.